This invention relates to novel ligand binding molecules and receptors, and to compositions and methods for improving the circulating plasma half-life of ligand binding molecules. In particular, this invention also relates to hybrid immunoglobulin molecules, to methods for making and using these immunoglobulins, and to nucleic acids encoding them.
Immunoglobulins are molecules containing polypeptide chains held together by disulfide bonds, typically having two light chains and two heavy chains. In each chain, one domain (V) has a variable amino acid sequence depending on the antibody specificity of the molecule. The other domains (C) have a rather constant sequence common among molecules of the same class. The domains are numbered in sequence from the amino-terminal end.
The immunoglobulin gene superfamily consists of molecules with immunoglobulin-like domains. Members of this family include class I and class II major histocompatibility antigens, immunoglobulins, T-cell receptor .alpha., .beta., .gamma. and .delta. chains, CD1, CD2, CD4, CD8, CD28, the .gamma., .delta. and .epsilon. chains of CD3, OX-2, Thy-1, the intercellular or neural cell adhesion molecules (I-CAM or N-CAM), lymphocyte function associated antigen-3 (LFA-3), neurocytoplasmic protein (NCP-3), poly-Ig receptor, myelin-associated glycoprotein (MAG), high affinity IgE receptor, the major glycoprotein of peripheral myelin (Po), platelet derived growth factor receptor, colony stimulating factor-1 receptor, macrophage Fc receptor, Fc gamma receptors and carcinoembryonic antigen.
It is known that one can substitute variable domains (including hypervariable regions) of one immunoglobulin for another, and from one species to another. See, for example, EP 0 173 494; EP 0 125 023; Munro, Nature 312: (Dec. 13, 1984); Neuberger et al., Nature 312: (Dec. 13, 1984); Sharon et al., Nature 309: (May 24, 1984); Morrison et al., Proc. Natl. Acad. Sci. U.S.A. 81:6851-6855 (1984); Morrison et al. Science 229:1202-1207 (1985); and Boulianne er al., Nature 312:643-646 (Dec. 13, 1984).
Morrison et al., Science 229:1202-1207 (1985) teaches the preparation of an immunoglobulin chimera having a variable region from one species fused to an immunoglobulin constant region from another species. This reference suggests molecules having immunoglobulin sequences fused with non-immunoglobulin sequences (for example enzyme sequences), however the reference teaches only immunoglobulin variable domains attached to the non-immunoglobulin sequence. Morrison et al., EP 0 173 494 teaches a similar chimera. While the term "receptor" is used by the authors, and the background section refers to "receptors such as immunoglobulins, enzymes and membrane proteins", the stated "receptors of interest" include "B-cell and T-cell receptors, more particularly, immunoglobulins, such as IgM, IgG, IgA, IgD and IgE, as well as the various subtypes of the individual groups" (page 3 lines 10-13). The disclosure of this reference is specific to immunoglobulin chimeras (see for example page 3, lines 21-30).
It has also been shown that it is possible to substitute immunoglobulin variable-like domains from two members of the immunoglobulin gene superfamily-CD4 and the T cell receptor-for a variable domain in an immunoglobulin; see e.g. Capon et al., Nature 337:525-531, 1989, Traunecker et al., Nature 339:68-70, 1989, Gascoigne et al., Proc. Nat. Acad. Sci. 84:2936-2940, 1987, and published European application EPO 0 325 224 A2.
A large number of proteinaceous substances are known to function by binding specifically to target molecules. These target molecules are generally, but need not be, proteins. The substances which bind to target molecules or ligands are referred to herein as ligand binding partners, and include receptors and carrier proteins, as well as hormones, cellular adhesive proteins, tissue-specific adhesion factors, lectin binding molecules, growth factors, enzymes, nutrient substances and the like.
Lymphocytes are examples of cells which are targeted to specific tissues. Lymphocytes are mediators of normal tissue inflammation as well as pathologic tissue damage such as occurs in rheumatoid arthritis and other autoimmune diseases. Vertebrates have evolved a mechanism for distributing lymphocytes with diverse antigenic specificities to spatially distinct regions of the organism (Butcher, E. C., Curr. Top. Micro. Immunol. 128, 85 (1986); Gallatin, W. M., et al., Cell 44, 673 (1986); Woodruff, J. J., et al., Ann. Rev. Immunol. 5, 201 (1987); Duijvestijn, A., et al., Immunol, Today 10, 23 (1989); Yednock, T. A., et al., Adv. Immunol, 44: 313-18 (1989)).
This mechanism involves the continuous recirculation of the lymphocytes between the blood and the lymphoid organs. The migration of lymphocytes between the blood, where the cells have the greatest degree of mobility, and the lymphoid organs, where the lymphocytes encounter sequestered and processed antigen, is initiated by an adhesive interaction between receptors on the surface of the lymphocytes and ligands on the endothelial cells of specialized postcapillary venules, e.g., high endothelial venules (HEV) and the HEV-like vessels induced in chronically inflamed synovium.
The lymphocyte adhesion molecules have been specifically termed homing receptors, since they allow these cells to localize in or "home" to particular secondary lymphoid organs.
Candidates for the lymphocyte homing receptor have been identified in mouse, rat and human (Gallatin, W. M., et al., Nature 303, 30 (1983); Rasmussen, R. A., et al., J. Immunol. 135, 19 (1985); Chin, Y. H., et al., J. Immunol. 136, 2556 (1986); Jalkanen, S., et al., Eur. J. Immunol. 10, 1195 (1986)). The following literature describes work which has been done in this area through the use of a monoclonal antibody, termed Mel 14, directed against a purported murine form of a lymphocyte surface protein (Gallatin, W. M., et al., supra; Mountz, J. D., et al., J. Immunol. 140, 2943 (1988); (Lewinsohn, D. M., et al., J. Immunol. 138, 4313 (1987); Siegelman, M., et al., Science 231, 823 (1986); St. John, T., et al., Science 231, 845 (1986)).
Immunoprecipitation experiments have shown that this antibody recognizes a diffuse, .about.90,000 dalton cell surface protein on lymphocytes (Gallatin, W. M., et al., supra) and a .about.100,000 dalton protein on neutrophils (Lewinsohn, D. M., et al., supra).
A partial sequence--13 residues--for a purported lymphocyte homing receptor identified by radioactively labeled amino acid sequencing of a Mel-14 antibody-defined glycoprotein was disclosed by Siegelman et al. (Siegelman, M., et al., Science 231, 823 (1986)).
Lectins are proteins with a carbohydrate-binding domain found in a variety of animals, including humans as well as the acorn barnacle and the flesh fly. The concept of lectins functioning in cell adhesion is exemplified by the interaction of certain viruses and bacteria with eucaryotic host cells (Paulson, J. C., The Receptors Vol. 2 P. M. Conn, Eds. (Academic Press, NY, 1985), pp. 131; Sharon, N., FEBS Lett. 217, 145 (1987)). In eucaryotic cell-cell interactions, adhesive functions have been inferred for endogenous lectins in a variety of systems (Grabel, L., et al., Cell 17, 477 (1979); Fenderson, B., et al., J. Exp. Med, 160, 1591 (1984); Kunemund, V., J. Cell Biol. 106, 213 (1988); Bischoff, R., J. Cell Biol. 102, 2273 (1986); Crocker, P. R., et al., J. Exp. Med. 164, 1862 (1986); including invertebrate (Glabe, C. G., et al., J. Cell. Biol. 94, 123 (1982); DeAngelis, P., et al., J. Biol. Chem. 262, 13946 (1987)) and vertebrate fertilization (Bleil, J. D., et al., Proc. Natl. Acad. Sci., U.S.A. 85, 6778 (1988); Lopez, L. C., et al., J. Cell Biol. 101, 1501 (1985)). The use of protein-sugar interactions as a means of achieving specific cell recognition appears to be well known.
The literature suggests that a lectin may be involved in the adhesive interaction between the lymphocytes and their ligands (Rosen, S. D., et al., Science 228, 1005 (1985); Rosen, S. D., et al., J. Immunol. 142(6): 1895-1902 (1989); Stoolman, L. M., et al., J. Cell Biol 96, 722 (1983); Stoolman, L. M., et al., J. Cell Biol. 99, 1535 (1984); Yednock, T. A., et al., J. Cell Biol. 104, 725 (1987); Stoolman, L. M., et al., Blood 70, 1842 (1987); A related approach by Brandley, B. K., et al., J. Cell Biol. 105, 991 (1987); and Yednock, T. A., et al., J. Cell Biol. 104, 725 (1987)).
The character of a surface glycoprotein that may be involved in human lymphocyte homing was investigated with a series of monoclonal and polyclonal antibodies generically termed Hermes. These antibodies recognized a .about.90,000 dalton surface glycoprotein that was found on a large number of both immune and non-immune cell types and which, by antibody pre-clearing experiments, appeared to be related to the Mel 14 antigen. (Jalkanen, S., et al., Ann. Rev. Med., 38, 467-476 (1987); Jalkanen, S., et al., Blood, 66 (3), 577-582 (1985); Jalkanen, S., et al., J. Cell Biol., 105, 983-990 (1987); Jalkanen, S., et al., Eur. J. Immunol., 16, 1195-1202 (1986).
Epidermal growth factor-like domains have been found on a wide range of proteins, including growth factors, cell surface receptors, developmental gene products, extracellular matrix proteins, blood clotting factors, plasminogen activators, and complement (Doolittle, R. F., et al., CSH Symp. 51, 447 (1986)).
A lymphocyte cell surface glycoprotein (referred to hereafter as the "LHR") has been characterized which mediates the binding of lymphocytes to the endothelium of lymphoid tissue. Full length cDNA clones and DNA encoding the human and the murine LHR (HuLHR and MLHR, respectively) have been identified and isolated, and moreover this DNA is readily expressed by recombinant host cells. The nucleotide and amino acid sequence of the human LHR (HuLHR) is shown in FIG. 1. The nucleotide and amino acid sequence of the murine LHR (MLHR) is shown in FIG. 2. Also provided are LHR having variant amino acid sequences or glycosylation not otherwise found in nature, as well as other derivatives of the LHR having improved properties including enhanced specific activity and modified plasma half-life, as well as enabling methods for the preparation of such variants.
It is shown herein that the LHR is a glycoprotein which contains the following protein domains: a signal sequence, a carbohydrate binding domain, an epidermal growth factor-like (egf) domain, at least one and preferably two complement binding domain repeat, a transmembrane binding domain (TMD), and a charged intracellular or cytoplasmic domain. The LHR of this invention contains at least one but not necessarily all of these domains.
A successful strategy in the development of drugs for the treatment of many abnormalities in ligand-binding partner interactions has been the identification of antagonists which block the binding or interaction between ligand and binding partner. One approach has been to use an exogenous binding partner as a competitive antagonist for the native binding partner. However, many ligand binding partners are cell membrane proteins which are anchored in the lipid bilayer of cells. The presence of membrane components is typically undesirable from the standpoint of manufacturing and purification. In addition, since these molecules are normally present only on cell surfaces, it would be desirable to produce them in a form which is more stable in the circulation. Additionally, even truncated or soluble ligand binding partners may not be optimally effective as therapeutics since they possess a relatively short in vivo plasma half-life, may not cross the placental or other biological barriers, and since merely sequestering their ligand recognition site without delivering an effector function may be inadequate for therapeutic purposes.
Accordingly, it is an object of this invention to produce ligand binding partners fused to moieties which serve to prolong the in vivo plasma half-life of the ligand binding partner, such as immunoglobulin domains or plasma proteins, and facilitate its purification by protein A. It is a further object to provide novel hybrid immunoglobulin molecules which combine the adhesive and targeting characteristics of a ligand binding partner with immunoglobulin effector functions such as complement binding, cell receptor binding and the like. Yet another object is to provide molecules with novel functionalities such as those described above for therapeutic use, or for use as diagnostic reagents for the in vitro assay of the ligand binding partners or their targets. It is another object to provide multifunctional molecules in which a plurality of ligand binding partners (each of which may be the same or different) are assembled, whereby the molecules become capable of binding and/or activating more than one ligand.
In particular, it is an objective to prepare molecules for directing ligand binding partners such as toxins, cell surface partners, enzymes, nutrient substances, growth factors, hormones or effector molecules such as the constant domain-like portions of a member of the immunoglobulin gene superfamily to cells bearing ligands for the ligand binding partners, and for use in facilitating purification of the ligand binding partners.
Another object of this invention is to provide ligand binding partner-immunoglobulin hybrid heteropolymers, especially heterodimers and heterotetramers, which are used in the targeting of therapeutic moieties to specific tissues and ligands. For example, a hybrid immunoglobulin consisting of one LHR-IgG chain and one CD4-IgG chain can be used to target CD4-IgG to tissues infected by viruses such as the human immunodeficiency virus (HIV). Similarly, a molecule having a ligand binding partner-plasma protein portion combined with a toxin-plasma protein portion is used to deliver the toxin to desired tissues.
It is another object to provide a method for expression of these molecules in recombinant cell culture.